This is a divisional of now abandoned application Ser. No. 09/021,861 filed on Feb. 11, 1998. This invention relates to a female metal terminal and a method of producing the same, and more particularly to a female metal terminal used to connect a wire harness and the like in an automobile, and a method of producing this female metal terminal.
Recently, for the purpose of protecting a driver and a passenger in the event of an emergency, safety devices, such as an air bag and a seat belt with a pre-tensioner, have been provided in an automobile. In a wire harness of such a safety device required to operate in the event of an emergency, there are used female metal terminals plated with gold of a good electrical conductivity, and in wire harnesses of other devices, there are used female metal terminals plated, usually, with tin, since gold is expensive. Thus, at least two kinds of female metal terminals, plated respectively with different materials, are suitably used in recent automobiles.
Generally, a female metal terminal includes a tubular proximal end portion, and a pair of resilient contact piece portions which are separated from each other by slits extending longitudinally from a distal end of the terminal to the proximal end portion, and are supported by the proximal end portion in a cantilever manner. This female metal terminal is decreasing in diameter progressively from the proximal end portion toward the distal end, and a constricted portion, provided at the distal end portion, serves as a contact portion. When a bar-like male terminal is inserted into the female metal terminal through the distal end thereof, the male terminal contacts the contact portion of the female metal terminal, thereby creating an electrical connection therebetween.
In the female metal terminal of the above construction, the longer the cantilever length of the resilient contact piece portions (supported in a cantilever manner) is, the lower the load of contact with the male terminal is, and in contrast, the shorter the cantilever length is, the higher the contact load is. Therefore, the cantilever length of the resilient contact piece portions of the female metal terminal plated with tin of a low electrical conductivity, is made shorter than the cantilever length of the resilient contact piece portions of the female metal terminal plated with gold of a high electrical conductivity, and by doing so, the load of contact of the tin-plated female metal terminal with the male terminal is made higher than that of the gold-plated female metal terminal.
U.S. Pat. No. 5,067,916 discloses a method of adjusting-a load of contact with a male terminal in accordance with a plating material applied to resilient contact piece portions of a female metal terminal. FIG. 9(a) is a developed, plan view of a conventional gold-plated female metal terminal 71 (in a pressed or stamped condition) disclosed in U.S. Pat. No. 5,067,916, and FIG. 9(b) is a developed plan view of a tin-plated female metal terminal 72 in a pressed condition.
As shown in FIGS. 9(a) and 9(b), the angle xcex81 between a tubular portion (proximal end portion) 73 and a resilient contact piece portion 74 of the gold-plated female metal terminal 71 is smaller than the angle xcex82 of a tubular portion (proximal end portion) 75 and a resilient contact piece portion 76 of the tin-plated female metal terminal 72. Namely, by changing the width of the proximal end portion of the resilient contact piece portion, the load of contact with the male terminal is adjusted in accordance with the plating material applied to the resilient contact piece portion of the female metal terminal.
As described above, in the recent automobile, several kinds of female metal terminals are required, depending on the electrical conductivity of the plating material applied to the surface of the female metal terminals. When providing the different female metal terminals by using the above method in which the contact load is adjusted by changing the length of the resilient contact piece portions, several kinds of dies are required for pressing or stamping the female metal terminals, and therefore the production process is cumbersome, and also the cost of the dies and the production cost are increased, and the handling is not easy. And besides, the length of the resilient contact piece portions differs depending on the plating material, and therefore it is necessary to prepare several kinds of housings, depending on this length, and this increases the production cost.
Furthermore, when the different female metal terminals are provided by using the method disclosed in U.S. Pat. No. 5,067,916, the only difference between the gold-plated female metal terminal and the tin-plated female metal terminal is that the proximal end portions of the resilient contact piece portions 74 and 76 are slightly different in width, and therefore the two kinds of female metal terminals have almost the same appearance, and also the dies for respectively forming these female metal terminals are almost the same, and therefore it is difficult to distinguish them from each other from the appearance, and not only a confusion but also a mistake may be involved in the production.
The present invention has been made in view of the above problems, and an object of the invention is to provide a female metal terminal and a method of producing the same, in which a load of contact with a male metal terminal can be adjusted in accordance with the electrical conductivity of a plating material applied to a surface of the female metal terminal, without changing a contour shape (including a length and a width) in a developed condition.
The object of the invention has been achieved by a method of producing female metal terminals plated respectively with gold and tin, comprising the steps of:
forming, by pressing, the female metal terminal which includes resilient contact piece portions, and a tubular portion supporting the resilient contact piece portions in a cantilever manner, a longitudinal cross-sectional shape of the resilient contact piece portions being changed so that a load of contact of the female metal terminal with a male metal terminal can be adjusted in accordance with electrical conductivity of a plating material applied to the female metal terminal, without changing a contour shape of the female metal terminal in a developed condition; and
forming the resilient contact piece portions and the tubular portion, formed by the pressing operation, into a tubular shape.
The object of the invention has also been achieved by a female metal terminal including resilient contact piece portions, and a tubular portion supporting the resilient contact piece portions in a cantilever manner, a longitudinal cross-sectional shape of the resilient contact piece portions being changed so that a load of contact of the female metal terminal with a male metal terminal can be adjusted in accordance with electrical conductivity of a plating material applied to the female metal terminal, without changing a contour shape of the female metal terminal in a developed condition.